a. Field of the Invention
This invention relates to improvements in de-reelers. These mechanisms, otherwise referred to as coil unwinders, wire feeders, etc. have a wide range of applications, and are especially useful in feeding welding wire from a coil to an automatic welding machine. In this application it is important that the material should be fed automatically upon demand at a rate corresponding to the rate of usage in the welding machine, and in such a manner that the wire is without twists or kinks, and without excessive tension being required to draw the wire material from the coil.
b. Description of the Prior Art
Machines which perform these functions have been known for some time, and can be classified according to the arrangement of the coil and the guiding device, i.e. whether the material is removed from the coil in a tangential direction, or in the axial direction of the coil. Such machines may be powered or unpowered. Where powered the motive force can be supplied by a rotary motor such as an electric or a fluid motor, or by a linear motor, e.g. a reciprocating pneumatic piston/cylinder unit.
Generally speaking, a power actuated de-reeler should be capable of:
1. detecting the demand for material to be fed,
2. accelerating the coil to the required speed to deliver the material therefrom,
3. maintaining the required speed as long as the demand is present, and
4. decelerating the coil when the demand ceases
Desirably the machine should be capable of operating over a wide range of speeds without the need for adjustment, should be able to avoid breakage of the material in the event that the machine malfunctions or fails to operate properly, should facilitate loading and/or unloading of the coil, and should be of low cost, and if possible portable
There have been numerous prior proposals for de-reeler machines, and a number of such machines are commercially available, but apparently for economic reasons have not found widespread use. De-reelers using rotary drive motors are relatively expensive because due to the large inertial forces that must be overcome in accelerating a heavy metal coil, e.g. of welding wire within the short time available, powerful and therefore expensive motors are required. De-reelers employing pneumatic or hydraulic linear actuator means, while generally lower in cost, also have a number of drawbacks, and in particular have generally required relatively large actuators capable of accelerating the coil to the required speed within a single stroke of the actuator.